Electric furnace.



C. HERING.

ELECTRIC FURNACE.

APPLICATION FILED MAY I. 1913.

(1,162,773, Patented 1590.7, 1915.

' 276;. 1 Wadi/A UZ jfl R3 CARL HERING, lOIF PHILADELPHIA, PENNSYLVANIA.

ELECTRIC FURNACE.

Specification of Letters Patent.

Patented Dec. 7, 1915.

Application led May 1, 1913. Serial No. 764,742.

To all 'whom it may concern Be it known that I, CARL HERING, a citizenof the United States, residing in the city of Philadelphia and State ofPennsylvania, have invented certain new and useful Improvements inElectric Furnaces, of which the following is a specification.

My invention relates to electric furnaces of the type in which a moltenor fluid resistor is involved; and relates more particularly to furnacesin which the resistors are so proportioned as to produce the pincheffect described in my prior Letters Patent of the United States No.988936. And my invention relates to features of electric furnaceconstruction of general application, though such features are moreparticularly valuable in connection with a pinch effect furnace.

By my present invention I provide furnace structure whichis especiallyapplicable to the heating of liquids or molten materials of relativelylow electrical resistivity, such as silver, gold, copper, etc. or alloysrich in such high conductivity materials; and which is applicable tocases in which it is desirable to have the hearth or bath containerdivided into tvvo or more compartments; and it is applicable to cases inwhich it is desirable to use treating current of relatively highervoltage and, therefore, proportionately less current, for a given amountof energy; and it is applicable to cases in which bottom pouring of theliquid or molten material is desirable. And my improved structure hasother advantages.

The hearth, bath container or melting chamber is divided into aplurality of compartments which are in communication with each other ator near the bottom of the fluid material through one or morecircumferentially closed, completely submerged channels completelyi'illed with the fluid or molten material. The electric current is madeto pass through the fluid or molten material in these channels whichlatter are so proportioned that the desired amount of heat is set freein the molten or fluid material within them; and the cross section ofthe channel or channels is so small relatively to the current passedthrough it that the resulting pinch effect keeps the fluid or moltenmaterial circulating rapidly enough to prevent any such overheating aswould cause rupture of circuit in the channel or channels, or as wouldcause any other undesirable state of affairs to arise. When the fluid ormolten material has been sufciently treated, it may be poured from achannel branching from and communicating with a heating channel, or maybe poured dir ctly from such a heating channel, or otherwise, thussecuring bottom pouring, which prevents slag, floating impurities orother undesirable matter from leaving the furnace with the pouredmaterial. Furthermore the fluid or molten material may be super-heatedimmediately before or While being poured.

The several compartments of the furnace hearth, bath containing chamberor melting chamber, may contain different slags if desired, for exampleone compartment may contain an acid slag and another a basic slag,whereby the material under treatment may be first subjected to theeffects of one of the slags of one compartment and then, without havingto change the slag or Without having to pour the material into anotherhearth or chamber containing another slag, may be subjected to the eectsof another slag. And by employment of a plurality of compartments, theymay have refractory linings of different materials, each adapted to theslag used in the particular compartment. Furthermore the total length ofthe combined resistor channels in which the heat is mainly generated,may be made greater, since the total length may be broken up intoseveral shorter separat/e'lengths and since one or more of the resistorchannels may be open at both ends; and with greater total length ofresistor channel the cross section of each channel may be made smaller,which features are particularly advantageous in the treatment of lowresistance materials such as above referred to.

My invention resides in the method and apparatus hereinafter describedand claimed.

For an illustration of some of the many forms my invention may takereference is to be had to the accompanying drawing, in which:

Figure 1 is a top plan view of a two compartment furnace embodyingfeatures of my invention. Fig. 2 is a vertical cross sectional viewtaken on the line X-X of Fig. 1. Fig. 3 is a side elevational view ofthe apparatus shown in Figs. l and 2. Fig. 4 is a top plan view of alive compartment furnace embodying features of my invention. Fig. 5 is aplan view of a three compartment furnace adapted for the application ofthree phase alternating current. Fig. 6 is a top plan view of a furtherform of furnace for the application of three phase alternating current.Fig. T is a top plan view of a third form of furnace applicable for athree phase alternating current. Fig. 8 shows several arrangements ot'resistors whereby circulation of the fluid or molten material may becaused to take place largely in one direction.l

Referring to Figs. l, 2 and 3, W represents the refractory wall orcontainer of refractory material of an electric furnace, such refractorymaterial being substantially a non-conductor of electricity, such aslire brick or other well known furnace material. 7Within the material lVare formed the two hearths, bath chambers or melting chambers H, Hcontaining the mass of material M, which, during the normal operation ofthe furnace, is fluid or molten metal, particularly a metal or alloy ofhigh electrical conductivity such as copper, silver, gold, brass, infact any metal or alloy.

E, E are electrodes through which current is communicated to thematerial M, these electrodes being either' vertical, as indicated infull lines or disposed in any other suitable position, for example,inclined, as indicated in dotted lines in F ig. 2. With the inner end ofeach electrode communicates a fluid resistor R, of material M,preferably at or near the bottom of the chamber lvl, communicatingtherewith, but at any rate completely submerged so that the resistor.forming channel C, circumferentially closed, is always maintainedcompletely filled with material M. And forming a communication betweenthe two hearths H, H are the resistors R', R in the channels C, C. rlhepath of current is then, in through one electrode E, through itsresistor l, through the main mass of material M in one of the hearths H,thence through the resistors it', R in succession to the material M inthe other hearth H, thence through the remaining resistor R to the otherelectrode E, it being understood that the terminals of the currentsource are connected to these electrodes E, E.

The cross section of each of the resistors R and R is so small, withrespect to the strength of the current passed through them, that thepinch eect ensues causing an automatic circulation, stirring oragitation of the material. And it will be seen that with the fourresistors in series with each other the total resistor length isrelatively great so that material of high electrical conductivity may besuccessfully treated without too greatly reducing the cross section ofthe resistors. And it is further apparent that by dividing the totalresistor length into a plurality of shorter resistors, each resistorwill not be so long as to interfere with the rapid circulation which isnecessary in order to prevent rthe material in the resistor fromreaching a temperature so high or excessive as to cause a rupture byvaporization, pinch effect or otherwise, in the material of theresistor, with attendant interference in operation and with damage tothe channel walls and to the furnace as a Whole. It is to be understoodhowever that the structure described is not limited in its use to lowresistivity materials, since the resistors both as to their length andcross section may be suitably proportioned for the treatment ofmaterials of high resistivity. And by the arrangement of resistorsdescribed, due to their great total combined length and to the greaterlength relatively to the cross section, whatever the material may bewhich is operated upon, the electrical energy may be delivered to theelectrodes E, E at relatively higher voltage and thereforeproportionately lower current strength, which among other advantagesdiminishes the loss of energy in the electrodes.

Communicating with both resistors R', R is a pouring hole P leading tothe pouring lip or spout S. By this construction when the material M isready for pouring, the furnace may be tilted, and the poured material isthen that of highest temperature, or at any rate of a temperature higherthan the main mass M in either hearth H, since the hole or channel Pcommunicates directly with a resistor channel. Furthermore the bottompouring thus made available insures that only clean metal or material Mwill be poured, as the slags, floating impurities, or other undesirablematerials will remain floating upon the main bath M in the hearths H, H,and will therefore be retained in these hearths.

Just before the pouring, or during the pouring, the strength of thecurrent passed through the resistors may be increased so as to superheatthe material or metal M before or during the pouring, with the resultthat the material or metal M poured will remain fluid a longer timeafter pouring and will more easily liow into and properly fill a mold.

To prevent waste or loss of heat from the baths M, M the cover A,omitted from F ig. l, may be provided as in Figs. 2 and 3 to cover thehearths or chambers H, H.

The mass of material M in the hearths H, ll may be more or less mixedwith each other, as by tilting the furnace as indicated b v the dottedlines in F ig. 3. the tilting be'- ing effected in this case by tippingthe furnace upon its rounded bottom. Obviously however the tilting maybe accomplished by pivoting the furnace and tilting it upon its istpivots; and obviously the arrangement may be such that the furnace maybe tilted not only in one plane but in planes at right angles to eachother-,or in all planes. In any event the sidewise tilting willraiseyone hearth higher than the other and in consequence there,will bea flow of material M from the higher hearth to the lower hearth throughresistors R. R, backward and forward according to the direction oftilting. This mixing of the materials in the two hearths is alsoattainable due to the pinch effect produced in the resistors R', R',causing more or of the circulating material to mix at the junction ofthese resistors. The pinch effect itself sometimes produces a higherlevel in one compartment and a lower one in the other, thus causing somemixing without tilting.

The channels C, C constitute in effect a single channel open at bothends, that is, communicating at both ends with a mass of material in ahearth or chamber. lith such a channel open at both ends the circulationof the material within the channel is chiefly outward from the channelat each cnd of the channel along its axis, and inward at each end of thechannel along the periphery of the channel. In consequence, such achannel, open at both ends, may therefore be made substantially twice aslong as a channel or resistor closed by or terminating at one end by anelectrode, as in the case with the resistors and channels R, R and C. C.In consequence, such a resistor channel` open at both ends, and ofsubstantially double the length of the resistor channel closed at oneend` will operate. without materially overheating the material. Inconsequence' such a channel, open at both ends, is better adapted fortreatment of low resistance materials or metals, like copper and itsalloys, or other materia-l hereinbefore referred to, with which, toobtain the necessary resistance for the liberation of the necessaryheat, a channel closed at one end would become so long that theattending pinch effect would not be able to carry the material out ofthe channel fast enough or before it was raised to dangerously hightemperatures.

rl`his structure lends itself to the employment of relatively highervoltages, as above explained. whereby the losses of energy in theelectrodes are reduced; and whereby the necessary energy may betransmitted to the electrodes with correspondingly less loss externallyto the electrodes and furnace. Furthermore with a plurality ofcompartments H, H, different slags may be used. For eX- ampleas forrefining steel, an acid slag may be used in one compartment, while abasic slag is used in another, thereby .avoiding the need for changingslags and saving heat that would otherwise be lost in changing slags.And since hearth or chamber linings of different materials are bestsuited to uses with different slags, by my arrangement of a plurality ofcompartments, each compartment may be lined with a ,material mo-stappropriate to the slag to be used in that compartment. Furthermore, alfresh and therefore more active slag may be used inl one compartmentfor acting upon or getting out the impurities in the bath, while astaler, previously used or less active slag may be used in anothercompartment to do the gross preliminary refining and to remove or actupon the larger part of the impurities. Furthermore by usingl aplurality of compartments, cold metal or raw material may be inserted inone compartment for melting, while another compartment may be used forthe refining by slag or other treatment, with the result that meltingand refining may be simultaneously carried on, making the process acontinuous one` and thereby avoiding freezing or chilling of the slagwhen cold metal or raw material is introduced.

In Fig. -l is shown in top plan view a furnace having features abovedescribed. Here the electrodes E, E communicate directly or throughsuitable resistors R, R with the baths in the chambers or compartmentsIl. H which in turn communicate through resistors R2, R2 in channels C2,C2, with the baths in compartments or chambers H1, IP. And between thebath in the compartment or chamber H2 and the baths in the compartmentsH1. H1 communication is afforded by resistors R3, R3 in the channels C3,C3. The channels C2 and C3 are of course always completely filled withfluid or molten material as described in connection with Figs. 1 to 3inclusive` and lie preferably at or near the bottom of the baths. Thepouring channel P in this case communicates with the bath in the chambereither at or near its bottom, or at the top. By this arrangement stillgreater total length of resistor may be obtained, while making practicaluse of the heating and pinch effect in each resistor. Obviously thenumber of resistors and number of baths may be further increased in anysuitable number and manner.

In Fig. 5 is shown in plan view a form of my furnace having the threeelectrodes-E1. E2 and E3 to be connected to any suitable source ofcurrent, such as a transformer or generator delivering three phasealternating current. For example these three electrodes may be connectedto the terminals of either a delta or Y connected source of three phasecurrent. These electrodes connect by resistors R with the baths in thethree compartments H1, H2 and H3 which are connected by the resistorsR1, R2 and R3, the pouring channel P communicating with the latter andleading to the pouring spout S. A somewhat similar arrangement is shownlll in Fig. 6. Here however the resistors R1, R2 and R3 come to a.junction with which the pouring channel P communicates. Here again theelectrodes may be connected to any suitable source of current, such as asource oIl three phase alternating current, either Y or delta connected.

ln Fig. 7 are shown three pairs of electrodes and three pairs ofresistors and three compartments or chambers, with one of them, forexample H8, communicating with the pouring channel P leading to the lipor spout S. The baths in the three chambers or compartments communicatewith each other through the resistors R1, R2 and R8 while the resistorslt form communication between the electrodes and the baths in thehearths or chambers. One pair ofz electrodes, as El, El may be connectedwith any suitable source of current, direct or alternating, or with onephase of a three phase source, and similarly the pair of electrodes E2,E2 may communicate with another source, or with another phase of a threephase source; and similarly the electrodes E3, EB may communicate withany suitable source of current, as a third phase of a three phasesource.

ln all of the structures above described all the resistor channels havebeen assumed to he of constant cross section throughout their length.and all of equal cross section. nd it is preferred that the channelswhich are open at both ends be substantially twice as long as anyresistor which is closed at one end as by an electrode. However myinvention is not to be understood as so limited, 'for the diflercntresistors may diHer among themselves as to cross section or length, orboth; and it is to be further understood that any or all of theresistors may change in cross section from end to end. And by suitablyshaping the resistor channels, especially those open at both-ends` thedirection of circulation caused by the pinch effect produced therein maybe largely in one direction. For example in Fig. 8 the resistor channelis either conical, that is, tapering in cross section, or is composed ofseveral parts inclined to each other with the result that thecirculation of molten material or flow therethrough tends to be strongerin one direction than in the other.

What l claim is:

l. 'lhe method of treating molten metal of high conductivity, whichconsists in confining the molten metal in one or more circumferentiallyclosed channels communicating with a plurality of separate masses of thematerial, passing current through the material in said channel orchannels, the channel diameter being small with respect to the channellength, and the current passed through the material in the channel'orchannels being great with respect to the channel cross section, wherebythe pinch effect is produced.

2. The method of electrically treating molten material, which consistsin confining said material in masses in communication with each otherthrough a portion of said material confined in a circumferentiallyclosed channel filled with said material, passing through the materialconfined in said channel an electric current whose strength is greatwith respect to the cross section of said confined material, whereby thepinch efi'ect is produced in said confined material, thereby stirringsaid masses of material, and changing the level of a mass of saidmaterial to cause a fiow of material between masses through saidchannel.

3. 'lhe method of electrically treating molten material, which consistsin conning said material in masses in communication with each otherthrough a portion of said material confined in a circumferentiallyclosed channel filled with said material, passing through the materialconfined in said channel an electric current whose strength is greatwith respect to the cross section ot said confined material, whereby thepinch effect is'produced in said confined material, thereby stirringsaid masses of material, and subjecting the diiierent masses of materialto dii'ereut re-agents.

4. irl`he method of electrically treating molten material, whichconsists in confining said material in masses in communication with eachother through a portion of said material confined in a circumferentiallyclosed channel filled with said material, passing through the materialconfined in said channel an electric current whose strength is greatwith respect to the cross section of said confined material, whereby thepinch effect is produced in said confined material, thereby stirringsaid masses ot material, and treating one osaid masses of material withre-agent and introducing raw material into another of said masses.

rlhe method of treating molten iron or steel, which consists inconfining said iron or steel in masses in communication with eachthrough a circumferentially confined mass of iron or steel, and passingthrough said confined molten iron or steel an electric' current Whosestrength is great with respect to the cross section of said confinedmolten iron or steel, whereby the pinch eect is produced in saidconfined molten iron or steel, and thereby stirring said masses ofmolten iron or steel, treating one of said masses of molten iron orsteel with at basic slag, and treating another of said masses of molteniron or steel with an acid slag.

6. The method of electrically treating molten material, which consistsin confining said material in masses in communication with each otherthrough a portion of said material confined in a circumferentiallyclosed channel filled with said material, and passing through thematerial confined in said channel an electric current Whose strength isgreat with respect to the cross section of said confined material,whereby the pinch effect is produced in said confined material, therebystirring said masses of material, treating one of Said masses ofmaterial with fresh or active re-agent, and treating another mass ofsaid material with a artly spent re-agent.

The method of treating molten material, Which consists in confining saidmolten material in masses in communication With each other through arestricted section of said material, passing current through saidrestricted sectioniof material to heat and move the same to cause amixing of said masses through said restricted section, treating one ofsaid masses of molten material with a re-agent, and treating another ofsaid masses of material with a different re-agent.

8. The method of treating molten material, which consists in confiningsaid molten material in masses in communication With each other througha restricted section of said material causing a mixing of said massesthrough said restricted section, treating one of said masses of materialwith a fresh or active re-agent, and treating another of said masses ofmaterial With a partially spent reagent.

9. The method of treating molten material, which consists in confiningsaid molten material in masses in communication with each other througha restricted section of said material, passing current through saidrestricted section of material to heat and move the same to cause amixing of said masses through said restricted section, and

adding raw material to one of said masses.

10. The method of treating molten material, Which consists in confiningsaid molten material in masses in communication with each other througha restricted section of said material, passing current through saidrestricted section of material to heat and move the same to cause amixing of said massesthrough said restricted section, adding rawmaterial to onel of'said masses, and treating another of said massesWith a reagent.

11. The method of treating molten material, which consists in confiningsaid molten material in masses in communication with each other througha plurality of serially connected restricted sections of said material,and passing current through said restricted sections of material to heatand move the same tocause a mixing of said masses through saidrestricted sections.

12. The method of treating molten material, Which consists in confiningsaid molten material in masses in communication Vmove the same to causea mixing of said masses through said restricted sections, treatmg one ofsaid masses of molten material with a re-agent, and treatmg another ofsaid masses of material with a different agent.

13. The method of treating molten material, which consists in confiningsaid molten material in masses in communication with each other througha restricted section of said material causing a mixing of said massesthrough said restricted section, treating one of said vmasses ofmaterial with a fresh or active re-agent, and treating another of saidmasses of material with a partially spent reagent, and passing anelectric current through said restricted section of material.

1li. The method of treating molten material, which consists in confiningsaid molten material in masses in communication with each other througha plurality of serially connected restricted sections of said material,passing current through said restricted sections of material to heat andmove the same to cause a mixing of said masses through said restrictedsection, adding rau7 material to one of said masses.

15. The method of treating molten material, which consists in confiningsaid molten material in masses in communication with each other througha plurality of serially connected restricted sections of said material,passing current through said restricted sections of material to heat andmove the same to cause a mixing of said masses through said restrictedsections, adding raw material to one of said masses, and treatinganother of said masses With a reagent.

16. An electric furnace comprising two or more chambers adapted tocontain molten material, means affording mechanical and electricalcommunication between the molten material in said chambers comprisingcircumferentially closed channels located below the level of said moltenmaterial and communicating with said chambers, a source of currentexternal to said furnace, electrodes connected to said source of currentand to said molten material, the cross section of a channel being suchthat the density of the current in the molten material in said channelis such as to cause so rapid a circulation of molten material in saidchannel by the pinch effect that dangerous temperatures in said channelare prevented.

17. An electric furnace comprising tWo or more chambers adapted tocontain molten material, electrodes for conducting electric current intosaid molten material, a circumferentially closed channel connecting anelectrode through the molten material in said channel with the moltenmaterial in a chamber, and a circumferentially closed channel connectingchalnbers with each other, the molten material in said channels andchambers forming a closed electric circuit including said electrodes.

18. An electric furnace comprising two or more chambers adapted tocontain molten material, electrodes for conducting electric current intosaid molten material, a circumferentially closed channel connecting anelectrode through the molten material in said channel with the moltenmaterial in a chamber, and a circumferentially closed channel connectingchambers with each other, the molten material in said channels andchambers forming a closed electric circuit including said electrodes,the current through one or more of said channels being so great withrespect to the cross section thereof that rapid circulation of saidmolten material is produced therein by the pinch effect.

19. A tilting electric furnace comprising circumferentially closedresistor channels constituting sole communication between separatedchambers, said chambers adapted to contain molten material filling saidchannels, means for passing current through the material in saidchannels, and a pouring outlet connecting with a channel.

20. An electric resistance furnace comprising electrodes, and a circuitWithin said furnace having said electrodes as4 terminals, said circuitcomprising molten conducting material disposed in circumferentiallyclosed channels alternating with chambers, the current in the moltenmaterial in a channel being so great relatively to the cross sectionthereof that rapid circulation of said molten material is producedtherein by the pinch effect.

21. A tilting electric furnace comprising a resistor included in circuitwith electrodes, said resistor comprising molten conducting materialdisposed in a circumferentially closed channel having a plurality ofenlargements constituting crucibles or hearths open at the top, saidresistor forming the sole communication between said crucibles orhearths, and a pouring connection with said resistor.

22. An electric furnace comprising a plurality of hearths,circumferentially closed channels communicating with and connecting saidhearths in series below the level of molten conducting materialcontained in said hearths, and channels connecting each of the l.twohearths forming the ends of the series with electrodes.

23. An electric furnace for treatment of molten metals of highconductivity comprising a resistor of molten high conductivity metaldisposed in a circumferentially closed channel having a pluralityof-enlargements constituting crucibles or hearths, the diameter of thechannel being small compared to its length, and means for passingcurrent through the resistor material, said current being great withrespect to the cross section of the resistor, whereby the pinch effectis produced.

2-l. In an electric furnace a plurality of electrodes, a plurality ofsections of molten resistor connected in series with each other betweensaid electrodes, masses of molten material between resistor sections,said resistor sections adapted to have produced therein the pincheffect.

25. A tilting electric furnace comprising a circumferentially closedresistor channel constituting sole communication between separatedchambers in all positions of said furnace, said chambers adapted tocontain molten material filling said channel, means for passing currentthrough the material in said channel, and a pouring outlet connectingwith said channel.

26. A tilting electric furnace comprising circumferentially closedresistor channels constituting sole communication between separatedchambers in all positions of said furnace, said chambers adapted tocontain molten material filling said channels, means for passing currentthrough the material in said channels, and a pouring outlet connectingdirectly with a channel.

27. An electric furnace comprising a plurality of chambers, resistorchannels each opening at opposite ends into different of said chambersand forming means of communication between said chambers. and means forpassing current of the different phases of a polyphase source throughthe material in said different resistor channels.

28. An electric furnace comprising a plurality of chambers, resistorchannels interconnecting all of said chambers, said chambers andchannels forming a closed loop system, and means for passing currentthrough the material in said channels.

29. An electric furnace comprising a plurality of chambers, resistorchannels interconnecting all of said chambers, said chambers andchannels forming a closed loop system, and means for passing polyphasecurrent through the different parts of said loop system.

30. An electric furnace comprising a plurality of chambers, resistorchannels interconnecting all of said chambers, said chambers andchannels forming a closed loop system, electrodes, and channel resistorsforming connections between said electrodes and said loop system.

31. An electric furnace comprising a plurality of chambers, resistorchannels interconnecting all of said chambers, said chambers andchannels forming a closed loop system, means for passing current throughthe material in said channels, and a pouring outlet connecting with achannel.

32. The method of treating molten material, which consists in confiningthe molten material in one or more circumferentially closed channelsforming sole communication between a plurality of separated masses ofsaid material, passing current through the material in said channel orchannels to heat the same, and pouring material directly from a channelduring passage of current therethrough, whereby said material as it ispoured is at higher temperature than the material in said masses.

33. The method of treating a mass of molten material, which consists inconning a part of the material in a circumferentially closed channel orchannels forming a molten resistor or resistors, passing current throughsaid resistor or resistors to heat the same, substantially all of theheat communicated to the mass of material being generated in saidresistorl or resistors, pouring material directly from one or more ofsaid resistors during the passage of current therethrough. In testimonywhereof I have hereunto afliXed my signature in the presence of the twosubscribing witnesses.

CARL HERING. Witnesses: v

ELEANOR T. MCCALL, NELLIE EVANS.

